Signs of Vitamin D Deficiency: Symptoms, Thresholds, Who to Test

The signs of vitamin D deficiency the NHS lists are those of softening bone: pain in the back, shoulder, ribs, pelvis or legs, swollen and painful wrists, changes in the way you walk, difficulty climbing stairs or getting out of a chair because of weak muscles, tingling, cramping or twitching of the muscles, and breaking bones more often or after a minor accident; in children, bowed legs, small size and late teeth.¹ Tiredness, low mood, hair loss and frequent colds are not on the NHS list and have many other causes. What settles it is a blood test for 25-hydroxyvitamin D: in the UK, below 25 nmol/L is deficient, 25 to 50 may be insufficient for some people, above 50 is sufficient for most. In the National Diet and Nutrition Survey, 31% of adults aged 19 to 64 were below 25 nmol/L in January to March (Table 6.15), about one in six across the year,² so if you have the bone or muscle signs and are in a risk group, ask for the test.³

• Early signs: usually none: most people with a low level feel nothing
• Bone and muscle signs (NHS): deep pain in the back, shoulder, ribs, pelvis or legs, swollen wrists, weakness climbing stairs or rising from a chair, cramps and twitching
• Severe and prolonged: softened bones, fractures after minor accidents, a changed walk; in children, bowed legs, poor growth, late teeth
• Threshold: below 25 nmol/L deficient; above 50 sufficient; UK tests report nmol/L
• Correction: levels settle over about two months of daily dosing; bone, muscle or joint pain eases "usually after a few weeks or months" (NHS)

What vitamin D deficiency feels like

Most people with low vitamin D feel nothing specific, which is why the NHS gives a supplement rule rather than a symptom check. When symptoms come they are in bone and muscle: a deep, dull pain in the back, shoulder, ribs, pelvis or legs, swollen and painful wrists, and weak muscles that make climbing stairs or getting out of a chair difficult, sometimes with tingling, cramping or twitching, a changed walk, and bones that break "more often or after a minor accident".¹ Tiredness, low mood, hair thinning and frequent colds are not on the NHS list; pooled trials found no change in depression scores and, in the 2025 update, no significant drop in respiratory infections.⁴ In children, the picture is rickets: bowed legs, swollen wrists and ankles, delayed walking, poor growth and late teeth.^{1, 5} UK surveillance found about one case of rickets per 200,000 children a year, 1.39 per 100,000 under five, mostly in Black and South Asian children, and 77.6% of them were not taking the supplement they were eligible for.⁶

Why the signs cannot diagnose you

Because bone and muscle pain are shared with many conditions, and the tiredness and low mood people search for come as readily from iron deficiency, B12 deficiency, an underactive thyroid, poor sleep or depression. A symptom list points to a blood test as well as the standard 10 microgram supplement, and the sensible request is for vitamin D alongside a full blood count, ferritin, B12, folate and thyroid function, because the causes often travel together. Our vitamin D guide covers units and dose.

The blood test and the UK thresholds

The test measures 25-hydroxyvitamin D, the storage form, in nanomoles per litre. UK guidance from the Scientific Advisory Committee on Nutrition and the NHS: below 25 nmol/L is deficient and associated with rickets and osteomalacia; 25 to 50 nmol/L may be insufficient for some people, particularly for bone; above 50 nmol/L is sufficient for most people.^{7, 8} American sites use ng/mL; 1 ng/mL is 2.5 nmol/L.

Your GP can test it, and will if you have symptoms, risk factors or a bone condition; the NHS does not screen people without symptoms. How to check your vitamin D levels explains the test.

Who should ask for a test?

Anyone with the bone pain or muscle weakness above. People in the groups the NHS advises to supplement all year who have not been: those who are housebound or in care, who cover their skin outdoors, or who have darker skin. People with malabsorption, including coeliac disease, Crohn's disease and after bariatric surgery. People on long-term anti-epileptic medicines or steroids. People with osteoporosis, a fragility fracture or kidney or liver disease. Pregnant and breastfeeding women with symptoms. Children with bowed legs, delayed walking or poor growth, urgently.^{1, 3}

How do I know if my child is lacking vitamin D?

Usually you cannot tell from looking, which is why the NHS gives a supplement rule for babies and children rather than a symptom check: "Children aged 1 to 4 years old should be given a daily supplement containing 10 micrograms of vitamin D throughout the year", and babies up to one year need 8.5 to 10 micrograms a day unless they have more than 500 ml of formula a day.⁹ The signs the NHS lists for rickets are bowed legs, swollen and painful wrists, being small for their age, teeth coming through later than usual and changes in the way a child walks; "If a GP thinks you or your child may have rickets or osteomalacia, they'll check your vitamin D and calcium levels", so a child with any of these needs a GP, not a home test.¹

How quickly can you fix it, and how long until you feel better?

Blood levels rise over several weeks of daily dosing: 25-hydroxyvitamin D has a half-life of two to three weeks, so it takes about two months to settle at a new level, and NICE does not routinely re-test people on a maintenance dose.³ For mild deficiency, the standard 10 micrograms a day may be enough; for confirmed deficiency, your GP decides the treatment dose, and the adult upper limit from supplements is 100 micrograms a day.⁷ The NHS says bone, muscle or joint pain from low vitamin D is "likely to get better when your vitamin D levels are normal again", "usually after a few weeks or months";¹⁰ vitamin D holds bone steady rather than adding density, which is loading exercise's job, as can you rebuild bone density explains.

Weight, sleep and the questions people ask

Does vitamin D deficiency cause weight gain? No. Higher body weight lowers vitamin D levels, because the vitamin is diluted in a larger body; correcting deficiency does not change weight.

Can low vitamin D affect sleep? Across nine observational studies of 9,397 people, low vitamin D went with 1.5 times the odds of a sleep disorder, and three pooled randomised trials improved a sleep quality score by 2.33 points, moderate certainty, while other sleep outcomes were not unanimous; no sleep claim is authorised for vitamin D.¹¹ Which vitamin deficiency affects sleep has the pooled trials.

Does vitamin D deficiency cause hair loss? Hair loss is not on the NHS list; iron status and thyroid function are the usual tests.¹

Preventing it

The UK advice: 10 micrograms (400 IU) a day for everyone from October to March, all year for the risk groups, with summer sun in the UK on bare arms without burning and oily fish, eggs and fortified foods for a few micrograms more. Which foods are highest in vitamin D has the UK portions; what vitamin D3 is good for covers the form. Vitamin D contributes to the maintenance of normal bones and teeth, normal muscle function and the normal function of the immune system.

When to see a doctor

Bone pain, muscle weakness, a fracture after a minor fall, symptoms in a risk group, any child with bowed legs or delayed walking, and symptoms that persist after three months of a 10 microgram supplement. Also anyone on high-dose vitamin D with nausea, thirst, frequent urination or confusion, signs of too much; can you take too much vitamin D covers it.

What we don't know

• Whether levels between 25 and 50 nmol/L cause symptoms in otherwise healthy adults. Guidance treats them as possibly insufficient; evidence is mixed.⁷
• Whether correcting mild deficiency improves mood, sleep or immunity. Trials are inconsistent.^{4, 11}

Frequently asked questions

What are the 10 signs of low vitamin D?

The NHS lists bone pain, swollen painful wrists, changes in the way you walk, difficulty climbing stairs or getting out of a chair, muscle cramps and twitching, and bones that break after minor accidents; in children, bowed legs, being small for their age and late teeth. Tiredness, low mood, hair thinning and frequent colds are commonly reported and shared with many other causes, and are not on the NHS list, which is why the blood test decides.¹

How long does it take to correct low vitamin D?

Blood levels rise over several weeks of daily dosing: 25-hydroxyvitamin D has a half-life of two to three weeks, so it takes about two months to settle at a new level, and NICE does not routinely re-test people on a maintenance dose. Bone, muscle or joint pain eases "usually after a few weeks or months" (NHS).^{3, 10}

What happens if vitamin D is low for a long time?

Bones soften and fracture more easily (osteomalacia in adults, rickets in children), muscles weaken, and the parathyroid glands overwork. Treatment restores levels and eases pain; the NHS says bone changes such as bowed legs "may need further treatment", and some people need surgery, which is why it is worth finding early.¹

Sources

1. NHS. Rickets and osteomalacia (reviewed 9 July 2025). nhs.uk.
2. Office for Health Improvement and Disparities and Food Standards Agency. National Diet and Nutrition Survey 2019 to 2023, data tables chapter 6, Table 6.15 (25-hydroxyvitamin D by season, years 9 to 15 combined). gov.uk.
3. NICE CKS. Vitamin D deficiency in adults: diagnosis. cks.nice.org.uk; management, prevention. cks.nice.org.uk.
4. Jolliffe DA, et al. Vitamin D supplementation and acute respiratory infections: meta-analysis, 2025, Lancet Diabetes & Endocrinology. PubMed 39993397. Li G, et al. Vitamin D supplementation in depression in adults: systematic review, 2014, Journal of Clinical Endocrinology and Metabolism. PubMed 24423304.
5. Uday S, Högler W. Nutritional rickets and osteomalacia in the twenty-first century, 2017, Current Osteoporosis Reports. PubMed 28612338.
6. Julies P, et al. Nutritional rickets under 16 years: UK surveillance results, 2020, Archives of Disease in Childhood. PubMed 31949032.
7. Schoenmakers I, et al. Prediction of winter vitamin D status and requirements in the UK population, 2016, Journal of Steroid Biochemistry and Molecular Biology. PubMed 26970588.
8. NICE CKS. Vitamin D deficiency in children. cks.nice.org.uk.
9. NHS. Vitamin D (reviewed 3 August 2020). nhs.uk.
10. NHS. Common questions about colecalciferol (reviewed 10 January 2023). nhs.uk.
11. Gao Q, et al. Vitamin D deficiency and sleep disorders: meta-analysis, 2018, Nutrients. PubMed 30275418. Abboud M. Vitamin D supplementation and sleep: meta-analysis of intervention studies, 2022, Nutrients. PubMed 35268051.

This article is general information, not medical advice. Bone pain, muscle weakness, a fracture after a minor fall or any child with bowed legs needs a GP.